Shale oils produced by conventional retorting processes generally have pour points in the range from 65.degree. to 85.degree. F. (18.degree. to 29.degree. C.). Shale oil retorts, for economic reasons, are generally located near oil shale deposits and these are usually located in remote areas, such as Colorado. Since the temperature in these areas is frequently below freezing (32.degree. F., 0.degree. C.), high-pour-point shale oil cannot be handled at these low temperatures unless measures are taken to prevent the oil from being cooled below its pour point and setting up. Since it may be desirable to transport shale oil by pipeline or tank car from the retorting site to a location where it may be conveniently processed, it is especially important to be able to keep the shale oil from setting up while it is being transported. Various methods have been disclosed for lowering the pour point of shale oils and for making a shale oil blend having a lowered pour point, but the need remains for a simple, inexpensive method to make a low-pour-point shale oil blend.
U.S. Pat. No. 3,284,336 discloses that a heavy fraction separated from a crude shale oil can be thermally treated and blended with a light fraction to produce a low-pour-point oil. Although the heavy fraction, after thermal treatment, does not have a low pour point, it is claimed as a pour point depressant for petroleum oils or fractions.
U.S. Pat. No. 3,532,618 discloses a composition having a reduced pour point which comprises a shale oil having a pour point above 20.degree. F. and the asphaltene portion of a hydrovisbroken shale oil. Hydrovisbreaking is a different process from thermal treating. Hydrovisbreaking lowers the pour point predominantly by cracking paraffins in the oil, whereas thermal treating lowers the pour point by forming a pour point depressant.
U.S. Pat. No. 3,523,071 discloses that the high-boiling fraction of visbroken shale oil is effective in reducing the pour point of hydrodenitrogenated shale oil, but that it is not effective in reducing the pour point of a raw shale oil.
U.S. Pat. No. 3,738,931 discloses that a low-pour-point product can be made by visbreaking shale oil, separating and hydrogenating the visbroken vapors and recombining them with the visbroken liquid.
The above references demonstrate that the pour point of a shale oil composition cannot be predicted from a knowledge of the pour points of the individual components. Surprisingly and in spite of this unpredictability, I have found a shale oil composition which has a low pour point, and which is suitable for being transported in cold weather without fear of it setting up.